Portable navigation devices (PNDs) including GPS (Global Positioning System) signal reception and processing means are well known and are widely employed as in-car navigation systems. In essence, modern PNDs comprise:                a processor,        memory (at least one of volatile and non-volatile, and commonly both),        map data stored within said memory,        a software operating system and optionally one or more additional programs executing thereon, to control the functionality of the device and provide various features,        a GPS antenna by which satellite-broadcast signals including location data can be received and subsequently processed to determine a current location of the device,        optionally, electronic gyroscopes and accelerometers which produce signals capable of being processed to determine the current angular and linear acceleration, and in turn, and in conjunction with location information derived from the GPS signal, velocity and relative displacement of the device and thus the vehicle in which it is mounted,        input and output means, examples including a visual display (which may be touch sensitive to allow for user input), one or more physical buttons to control on/off operation or other features of the device, a speaker for audible output, -optionally one or more physical connectors by means of which power and optionally one or more data signals can be transmitted to and received from the device, and        optionally one or more wireless transmitters/receivers to allow communication over mobile telecommunications and other signal and data networks, for example Wi-Fi, Wi-Max GSM and the like.        
The utility of the PND is manifested primarily in its ability to determine a route between a start or current location and a destination, which can be input by a user of the computing device, by any of a wide variety of different methods, for example by postcode, street name and number, and previously stored well known, favourite or recently visited destinations. Typically, the PND is enabled by software for computing a “best” or “optimum” route between the start and destination address locations from the map data. A “best” or “optimum” route is determined on the basis of predetermined criteria and need not necessarily be the fastest or shortest route. The selection of the route along which to guide the driver can be very sophisticated, and the selected route may take into account existing, predicted and dynamically and/or wirelessly received traffic and road information, historical information about road speeds, and the driver's own preferences for the factors determining road choice. In addition, the device may continually monitor road and traffic conditions, and offer to or choose to change the route over which the remainder of the journey is to be made due to changed conditions. Real time traffic monitoring systems, based on various technologies (e.g. mobile phone calls, fixed cameras, GPS fleet tracking) are being used to identify traffic delays and to feed the information into notification systems.
The navigation device may typically be mounted on the dashboard of a vehicle, but may also be formed as part of an on-board computer of the vehicle or car radio. The navigation device may also be (part of) a hand-held system, such as a PDA (Personal Navigation Device) a media player, a mobile phone or the like, and in these cases, the normal functionality of the hand-held system is extended by means of the installation of software on the device to perform both route calculation and navigation along a calculated route. In any event, once a route has been calculated, the user interacts with the navigation device to select the desired calculated route, optionally from a list of proposed routes. Optionally, the user may intervene in, or guide the route selection process, for example by specifying that certain routes, roads, locations or criteria are to be avoided or are mandatory for a particular journey. The route calculation aspect of the PND forms one primary function provided, and the navigation along such a route is another primary function. During navigation along a calculated route, the PND provides visual and/or audible instructions to guide the user along a chosen route to the end of that route, that is the desired destination. It is usual for PNDs to display map information on-screen during the navigation, such information regularly being updated on-screen so that the map information displayed is representative of the current location of the device, and thus of the user or user's vehicle if the device is being used for in-car navigation. An icon displayed on-screen typically denotes the current device location, and is centred with the map information of current and surrounding roads and other map features being also displayed. Additionally, navigation information may be displayed, optionally in a status bar above, below or to one side of the displayed map information, examples of navigation information including the distance to the next deviation from the current road required to be taken by the user, the nature of that deviation possibly being represented by a further icon suggestive of the particular type of deviation, for example a left or right turn. The navigation function also determines the content, duration and timing of audible instructions by means of which the user can be guided along the route. As can be appreciated a simple instruction such as “turn left in 100 m” requires significant processing and analysis. As previously mentioned, user interaction with the device may be by a touch screen, or additionally or alternately by steering column mounted remote control, by voice activation or by any other suitable method.
A further important function provided by the device is automatic route re-calculation in the event that                a user deviates from the previously calculated route during navigation therealong,        real-time traffic conditions dictate that an alternative route would be more expedient and the device is suitably enabled to recognize such conditions automatically, or        if a user actively causes the device to perform route re-calculation for any reason.        
It is also known to allow a route to be calculated with user defined criteria; for example, the user may prefer a scenic route to be calculated by the device, or may wish to avoid any roads on which traffic congestion is likely, expected or currently prevailing. The device software would then calculate various routes and weigh more favourably those that include along their route the highest number of points of interest (known as POIs) tagged as being for example of scenic beauty, or, using stored information indicative of prevailing traffic conditions on particular roads, order the calculated routes in terms of a level of likely congestion or delay on account thereof. Other POI-based and traffic information-based route calculation and navigation criteria are also possible.
Although the route calculation and navigation functions are fundamental to the overall utility of PNDs, it is possible to use the device purely for information display, or “free-driving”, in which only map information relevant to the current device location is displayed, and in which no route has been calculated and no navigation is currently being performed by the device. Such a mode of operation is often applicable when the user already knows the route along which it is desired to travel and does not require navigation assistance.
Current map data providing companies such as TeleAtlas NV and NavTeq® produce digital map data in the form of one or more base data files from which the PND extracts information which is used in the creation of graphical representations of geographical features, such as roads, buildings, railroads, and other landmarks and POIs. This information is displayed on the screen of the device, and is refreshed almost continuously, to provide the user with a continuously changing map of the current location and surrounding area with reference to a generally stationery graphical vehicle indicator also displayed in the middle of the screen. The extent of the detail shown in the map is dependent on many factors including the particular scale of the map chosen by the user, the speed of travel, and of course the level of detail provided by the underlying map data files in use for the particular locality in which the device is currently situated. For example, only relatively little information may be displayed on the screen of the device when the user is traveling on a motorway through countryside, whereas relatively much greater levels of detail may be provided on-screen when the user is traveling through a city on congested roads, and thus quite slowly.
In this latter scenario, the navigation functionality provided by the device is enhanced by the display of more detailed information on-screen on account of the greater likelihood that the user can correlate road-side or road-based features displayed on-screen with the corresponding physical features which he can see as he drives along the particular road or roads in question. One disadvantage with current map provider-originated data files is that their level of detail only increases with every successive version release. As such, these occur only relatively infrequently, and therefore it is possible for map information to be outdated by changes in road layouts and the implementation of access limitations often occurring in cities and to a lesser extent, in extra-urban regions. Additionally, map data does not generally include transient road alterations, such as may be caused by road works; carriageway reductions or alterations, or pedestrianization of roads previously mapped as vehicular thoroughfares.
Indeed, as a result of the various processes used in the creation of digital map data, it is often the case that map data files installed in new PNDs and navigation systems already tend to be at least a year or so out of date by the time the device or system is delivered to the end user. Accordingly, the present applicant has developed MapShare™ technology in software provided on the device which affords the user the facility to identify a variety of corrections for immediate or subsequent transmission to validation, collation and/or other back-end, server-based processing at a centralized location. Transmissions of such map-specific, corrective information may be delivered by means of establishing a short-range wireless communication with a mobile telephone, usually using a Bluetooth® protocol thus enabling the device to transmit such information ultimately over a mobile telecommunications network.
Examples of the corrective information which may be stored and subsequently transmitted from the device (all of which information being geospatially tagged with specific location coordinates or a range of coordinates where a road or road segment is identified and desired to be corrected) are:
Street unblocking/blocking (i.e. making a previously un-enterable street enterable and vice versa), one-way direction reversal, street name data and property number/name data, addition or removal of POIs and POI data, the identification in map data of a new street/road or the removal of a map-data identified street which no longer exists, missing, incorrect or alternative city name data, new/redundant motorway entrance/exit data, missing/incorrect postcode information, roundabout addition/deletion, and other correction data for which simple, user-enterable description may be provided and does not fit into any other categories.
Additionally, it is possible to download corrections previously validated, to a greater or lesser extent depending on various categorization or user trust level types, from a centralized map data updates location. Such corrections may be downloaded either by means of connection of the device using a physical to a USB cable to an internet connected PC executing appropriate software which communicates both with the centralized server by means over the Internet and with the device over the cable, or wirelessly with a local mobile telephone.
Currently however, correction data which is downloaded is immediately stored on the device and applied to the underlying map data without any requirement for user interaction, such correction data being automatically assumed by the device to represent correct information.
It is an object of the present invention to provide a PND or navigation system, a method of operating such, and a computer program by means of which such are controlled which allows a PND or navigation system to provide enhanced map data correction.